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present study deals with the problem of determing drag force acting on spherical particles by slowII, EM-III, and EM-IV are presented to predict the drag on the spheres in random arrays. These predictions are com-pared with numerical simulations. The EM-IV model in which the volume exclusion effect near the representative sphereis taken into account in defining the effective-medium is found to compare very well with the numerical simulationsup to the volume fraction of spheres φ=0.5. In addition, Carman’s correlation is given for comparison. This empiricalcorelation is shown to be in god agreement with the simulation results beyond φ=0.4. Therefore, it is found that se-lective use of EM-IV and Carman’s correlation depending on φof the drag for full range of φ. Finally, the estimations are compared with the previous experimental results for the gaspressure drop across a micropacked bed reactor. The comparison shows a reasonable agreement between the experi-mental results and the estimations by Carman’s correlation.